Safety ejection control for casting machines



Feb. 14, 1967 J. D. MISLAN 7 SAFETY EJEGTION CONTROLS FOR CASTINGMACHINES Filed April '7, 1964 2 Sheets-Sheet l JOsEPH D. M/SLAN INVENTOQJ. D MISLAN 3,303,537

SAFETY EJECTION CONTROLS FOR CASTING MACHINES Feb. 14, 1967 2Sheets-Sheet 2 Filed April 7, 1964 359:0 96mm mm QEmWV EEC. ag i.

E g 2 3 5 N52? wm w Em I @0555 m5 ygzoFfim H J05 EPH D. M/SLAN wvewrarzUnited States Patent 3,303,537 SAFETY EJECTIGN CONTROLS FOR CASTINGMACHINES Joseph D. Mislan, Morrisville, Pa., assignor to Systems Matrix,llnc., a corporation of New Jersey Filed Apr. 7, 1964, Ser. No. 357,9568 Claims. (Cl. 22-94) This invention pertains to casting machines orpresses of the diecasting type, and particularly to arrangements bywhich the cyclic operation of the machine will be automaticallyinterrupted upon certain failures or disturbances in the normal sequenceof events associated with each casting or molding cycle; specifically,upon failure of complete ejection of the cast piece from between theplatens.

Conventional die-casting presses for the production of molded metalparts include a pair of plates or platens to which are securedrespective die members defining the molding cavities. One of theseplatens, at least, is arranged for movement (usually under hydrauliccontrol) between die-open and die-closed positions, and means areprovided for injecting molted casting metal into the cavities during thedie-closed part of the cycle. Thereafter, and after a time sufiicientfor the molded parts to have cooled to solid condition, the dies areseparated, and the molded part (or parts, in the case of a multicavitydie) is ejected in preparation for the next molding cycle.

Machines of this type are resigned to operate at high speeds on anautomatic cycle, and it is extremely important that their operation beinterrupted upon the occurrence of certain failures in the operation. Itis also desirable that a corresponding signal be given, for supervisorypurposes. No particular problems are presented in the sensing orverification of stages or events involving the motions or positions ofthe die blocks or platens, the injection apparatus, and other partswhich are permanent and relatively unchanging features of the machine.However, the same machine will from time to time be used to mold avariety of differently shaped parts, by the substitution of differentdie blocks, and even when this is not a factor, the problem of ensuringthat the molded part or parts be fully ejected from the dies is adifficult one.

Failure of the machine to fully eject the molded product, beforecommencement of the next cycle, can be very serious. Ejection is usuallyproduced by the operation of ejecting pins or strippers which areautomatically pushed into the die cavities during the opening(die-separating) movement of the platens. When thus loosened from thecavity, the part may then fall between the platens or dies into adelivery chute or the like. If a molded part is not fully ejected, or ifit is broken and only one portion falls free, the un-ejected solidmaterial will usually prevent complete closure of the die blacks duringthe succeeding cycle, and result in damage to the dies or their cores,and might under some circumstances cause the squirting of hot metal fromthe machine during the next molding cycle. Even if an un-ejected orbroken part remains in the cavity in such a way as not to interfere withthe closing of the dies, its presence in the cavity will prevent themaking of an acceptable molded piece on the next succeeding machinecycle. The control system further prevents continuation of idle dieclosing and opening cycles if no parts are being produced; for exampleif there is a failure of casting metal supply.

Attempts to provide a machine-control system that will meet the abovesituation have not been successful. For example, systems for sensing orcounting the ejected parts as they pass through or along the deliverychute or chan- 3,363,537 Patented Feb. 14, 1967 nel have been devised,using mechanical feelers or photoelectric sensors. Similar sensors havebeen arranged to sense the presence of molded pieces or sections in thecavity, after opening of the dies and the operation of the ejectingdevices. No dependable sensing system of any of these types has comeinto use, largely because of their requirement for highly criticaladjustment to meet the various situations that can arise (especiallywhen the dies are changed), the impossibility of detecting broken piecesof a molded part by physical contact or optical sensing, and othershortcomings.

The present invention is directed to a system for sensing any failure ofthe complete ejection of the molded product at the end of each machinecycle, quite independently of the particular shape or configuration ofthe part or parts, and of the number produced per cycle (that is, forexample, by a multi-cavity die). This is accomplished by sensing theradiant energy, particularly heat, proceeding from any molded materialretained in or by the dies themselves, during a period following theejection operation. It will be understood that in any machine of thiskind, the freshly molded parts, even after they have solidified, are ata higher temperature than the dies themselves, and particularly so forthe higher operating speeds in which it is desired to start the nextcycle with a minimum of delay after each injection phase. Hence, theretention of a molded part, or any broken piece, either in a cavity orin a partly ejected state, can be sensed by means of properly locatedsensors that are responsive to anomalies in the temperature or radiantenergy pattern resulting from the incomplete ejection of the molded partor parts.

In addition to the increased emission of radiation (heat or infra-redenergy) from any unejected parts due to their elevated temperaturerelative to the die and die cavity surfaces, it has been found that thereflectivity of the molded parts is appreciably greater, especially forenergy in the infra-red spectrum, than is the reflectivity of the dieand cavity surfaces. The invention therefore further contemplates alsothe sensing of unejected parts by reason of the selective reflection ofsuch energy' from their surfaces, when the open dies are flooded orbathed with incident heat rays or infra-red radiation from sourcesappropriately positioned relative to the open die parts.

In brief, the invention accomplishes its objects by providing one ormore infra-red sensing devices mounted on the molding press platens soas to respond to the heat energy or efiective temperature of the die andcavity surfaces, and of any molded material therein or therebet-ween, incombination with circuits for utilizing the output signals of suchdevices only during the proper portion of the machine cycle (that is,following the opening of the dies and the operation of the normalejection or stripping instrumentalities) for shutting down the machinewhen any molded material has not been fully ejected; and optionally forgiving an appropriate signal to the machine operator.

The invention will now be described in connection with a typical andpresently preferred illustrative embodiment thereof, given byway ofexample and not for purposes of limitation, and illustrated in theaccompanying drawings, in which:

FIG. 1 is a fragmentary perspective view of a typical installation ofthe sensing system applied to a conventional die casting machine.

FIG. 2 is a sectional view of one of the infra-red sensin-g devices usedin the invention.

FIG. 3 is a schematic Wiring diagram of the chosen form of arrangement.

Referring first to FIG. 1 of the drawings, the framework of a typicaldiecasting press is indicated by reference numeral 10, said frameworksupporting the usual fixed platen 12 provided with T-slots forsupporting there on one of the die blocks 14. The complementary dieblock is indicated at 16, mounted upon the moving platen 18, it beingunderstood that the die blocks contain or define the molding cavity intowhich the molten casting metal is injected under high pressure byconventional means which are not shown since they are well known tothose familiar with such presses. Numeral indicates one of the usual tierods which support and guide the moving platen during its movements toopen and close the die blocks, under the driving force of otherconventional parts which are also omitted for simplicity and clarity ofthe drawing. The injection of molten metal occurs under the control of amachine programming device, usually a form of timer or the like, and itis immaterial whether the metal is injected via a nozzle such asindicated at 13, leading through a passage in one of the die blocks andits associated platen, or through some different channel.

The platens 12 and 18 in FIG. 1 are shown in their separated or openposition, in which the retraction of platen 18 has carried the molded ordie-cast piece 22 to a position at which it would normally be ejected orstripped from the mold cavity in die block 16 as by a set of ejectingpins 24 fixed relative to the machine framework or resiliently mountedthereon so as to project into the die cavity when the platens separate,to engage and dislodge the molded piece which would then be removed frombeneath the die blocks in preparation for the succeeding closure of thedies and the molding of the next piece. As is apparent from the drawing,the molded piece 22 .has not been thus removed, and it is necessary toadvise the operator of this fact, and also to prevent the initiation ofthe next molding cycle, as by interrupting the further advance of themachine cycle programmer.

The invention accomplishes the sensing of the continued presence of anun-ejected workpiece by means of one or more, preferably several, heator infra-red radiation sensors 26 and 28, mounted upon the respectiveplatens 12 and 18 as by brackets bolted to them or to the existingT-slots thereof, but so arranged as not to physically interfere with theplaten motion. Each of these sensors has a radiation-receiving axis, andresponds to the infra-red radiation which it receives along such axis.Depending upon the shape and size of the pieces being molded, andwhether only one or both of the die blocks are such as might retain amolded piece against effective ejection, the sensors may be positionedand supported by one or both of the platens. In the typical installationshown in FIG. 1, one of the sensors is supported by each platen, anddirected so as to receive predominately the infra-red radiation from theexposed surface of the die block carried by the opposite platen. It willbe obvious that each sensor will receive radiation from the die block,whether or not the molded piece has been ejected; however, since the dieblocks themselves are always well below the melting temperature of themetal being cast, and since they open relatively soon after thesolidification of the injected metal, it will always be true that anyunejected workpiece will have a considerably higher temperature than thesurface of the empty die block, so that the sensors will produce asubstantially greater output signal in the instances where failure ofejection has occurred. For the same reason, if only a part of a castworkpiece is ejected, leaving a residual portion in a cavity or betweenthe die blocks, its presence will likewise produce a higher signaloutput from one or both of the sensors.

As mentioned earlier in this description, the sensors 26 and 28 willrespond to infra-red or heat radiation they receive, regardless ofwhether it is generated by the hot workpiece itself, or some unejectedportion thereof, or whether it is reflected by such workpiece or partfrom an external source of such energy. That is, the cast metal itselfhas a higher reflectivity for infra-red or heat radiation than do thesurfaces of the die blocks and any cavities therein. Therefore, it issometimes desirable to augment the detecting action by providing themachine with specific additional sources of infra-red energy directedtowards the sensed areas of the die block or blocks. Such sources areshown in FIGURE 1 as heat lamps or projectors 30 and 32, likewisesupported on the machine platens or framework out of the travel paths ofthe machine parts, and energized by any convenient source such as theusual 1l5-volt supply circuit. Preferably, the directional orientationof these sources is adjusted relative to the sensors 26 and 28 so that amaximum percentage of the applied infra-red radiation will be reflected,in a more or less specular manner, into the directional receiving axesof such sensors.

FIG. 2 shows in a longitudinal sectional View a typicai one of theinfra-red sensing devices, comprising for em ample a cylindrical casing34 within which is mounted, as upon the inner surface of the electricalconnector body 36, an infra-red sensing cell 38 such as a cadmiumsulfide or equivalent type whose resistance changes in response to itsexposure to infra-red radiation. Numeral 40 designates an optionalcooling or refrigerative mount for the sensitive cell to increase itssensitivity of response, and may be of the thermoelectric type or mayinclude a cit culating coolant if desired. In order to make the devicerelatively insensitive to light in the visible region, and thus to avoidfalse responses due to fortuitous changes in the ambient illumination, aselective infra-red transmit ting filter 42 may be added, and acondensing lens 44 of suitable infra-red transmitting glass ispreferably provided, as shown, to limit the acceptance angle of thedetector to radiation arriving predominately along the preferredsensitive axis of the device. 7

In order to integrate the ejection sensing circuits into the programcontrolling devices or timer of the press it= self, a circuitarrangement as shown in FIG. 3 may be employed. As an aid inunderstanding this diagram, it should be kept in mind-that in mostinstallations, the physical ejection pins or stripping means of thecasting machine will be associated with only one of the platen dies, thedies being designed to cause the molded part to follow a specific one ofthem during the die-opening move ment. Thus, during normal operation,the molded part should never stick in the opposite die, and if it shouldhappen to do so at any point in the opening travel of the moving platen,the machine cycle must be interrupted to prevent re-closure and asucceeding cycle. On the other hand, since the molded part will normallytravel with the other die block for at least a portion of its platentravel before the piece is subjected to the force of the ejectionmechanism, interruption of the cycle by sensing of that die should beinhibited until after such a delay as would ordinarily allow the moldedpiece to be ejected; in this way, stoppage of the machine is notproduced unless the molded piece, or a portion of it, remains in the dieafter the normal period for operation of the ejecting devices. Likewise,the operation will definitely be interrupted unless the molded piece issensed during die-opening movement; this prevents recycling if no pieceat all has been produced, as can happen if the injection apparatusfails.

Referring now specifically to FIG. 3, the detector 28 which is aimed atthe moving die block 16 is indicated at the left as an infra-redsensitive variable resistance connected between the base and emitter oftransistor Q1, with suitable bias resistors constituting it as anemitterfollower amplifier coupled through an adjustable resistance 50 toa second-stage emitter-follower transistor Q2, these amplifiers servingto raise the DC. level change, due to irradiation of sensor 28 (when itsenses a hot casting or fragment), to a value suitable for control ofthe typical Schmitt trigger formed -by interconnected transistors Q3 andQ4.

Power supply for the transistors is provided from a current source(battery or rectifier system, a battery being 5. shown for convenienceof illustraiton) 52 to terminal 54 over a pair of contacts 56 arrangedas a limit switch to be operated by the movement of the moving dieplaten 18; the arrangement is such that the contacts 56 close in advanceof the casting ejection instant, and remain closed at least untilcompletion of the ejection-sensing period. These contacts serve tointerrupt the power circuit long enough, following each cycle of relayoperations, to allow any relays held operated by holding circuits todrop out, or become de-energized, in preparation for the next sensingcycle. The sensing circuit is so arranged that when sensor 28 receivesinfra-red energy in excess of a level predetermined by the adjustment ofresistor 50, transistor Q3 is biased off or non-conducting,regeneratively switching transistor Q4 on and conducting current fromsource 52 through the coil of relay R1 to operate the same.

The Die Close timer 58 is a part of the casting machine control, and mayconsist of a timer motor or a delay solenoid operating a set of contactswhich control the operation of closing the platens, as well known in theart, so that closure can commence only a p-re-set time following theiropening, to allow time for ejection of the molded piece. Preventingclosure of the circuit of the timer 58 will therefore prevent the timerfrom comrnencing the next closing movement of the platens, and suchprevention is provided in the present arrangement by a seriesarrangement of the contacts of relays R1, R2, R3 and R4, all in serieswith the normal 115 volt A.C. supply line 60 of the timer 58.

Thus, as the moving die commences to open, contacts 56 close andenergize the supply circuits of the transistors. Sensor 28 initiallysenses the hot or reflective casting 22 in the moving die as the diesbegin to separate, and before the ejection mechanism becomes effective;transistor Q4 conducts, and relay R1 is energized, its normally opencontacts 62 closing a supply circuit 64 for relay R2, and the latteroperates and is held operated by the holding circuit 66. As the diescontinue to separate, the molded piece will normally 'be ejected fromdie 16, and relay R1 will release, but relay R2 will remain operated dueto its holding circuit. However, and even though contacts 68 of R1 and70 of R2 are both closed, the series circuit to the timer 58 will not becompleted until a third relay R3 is operated, by a momentary sensingpulse delivered to its coi-l from the condenser 72, via an adjustabletimer 74 which operates momentarily, following each operation ofcontacts 56, at a time at which ejection of the molded piece wouldnormally have been accomplished. Since relay R3 will thus be operatedmomentarily only at the proper sensing time, it will prevent the moldingcycle from recommencing even if relay R1 should drop out as a stuckcasting cools down. R3 acts as a gating circuit to'define the timeinterval during which the sensing is effective to establish either a goor no go condition, regardless of changes occurring outside thisinterval.

When relay R3 operates as described, and if contacts 68 and 70 areclosed as above described, the circuit of timer 58 is completed throughthe now-closed contacts 76 of relay R3 and the normally-closed contacts78 of relay R4, and a closing cycle of the platens is initiated.Obviously, if the molded piece had become stuck in the stationary die asthe dies opened, relay R1 would not have been operated at all, and relayR2 would also have not been energized, and the next closing cycle wouldbe inhibited at contacts 68 and 70. If, as sometimes happens, the moldedpiece is broken, and a part only is carried along in die 16 as it opens,the die-closing cycle might be initiated as above described, but in thiscase, the stationary die detector 26, and its associated circuitry 80 (aduplicate of the transistor portion of the moving die detector circuit)would energize relay R4 over conductor 82, preventing completion of thetimer 58 circuit at contacts 78. A holding circuit for relay R4 is shownover would remain open.

6. its contacts 84, to maintain the interruption of the timer circuituntil for example, a new cycle is initiated, after an operator clearsthe obstruction by a manual momentary-operated switch 86 overriding theinterruption of the circuit of timer 58.

Warning lamps 88, 90 may be connected for energization by the relays orany of them to signal to the operator the reason for any interruption ofthe closing cycle of the machine, and to provide adequate supervisionfor the system. It will be observed that the arrangement describedprovides a substantial measure of fail-safe protection, in thatcompletion of the circuit of timer 58 requires that, at the commencementof each opening of the dies, relay R1 first be operated to cause relayR2 to lock up. Without this preliminary operation of these relays, thetimer circuit could not be completed at all, because contacts 70 Hence,a failure of the sensing device 28, or the transistor circuits, willalso prevent reclosure of the dies in a positive manner.

An additional feature in the nature of a fail-safe provision resultsfrom the positive requirement that relay R1 operate (pull up) prior tothe instant or period (set by timer 74) when the go/no-go conditionrelative to casting ejection is determined. Thus, the sensors 26 and 28are looking at the dies even before they open. If the die temperaturesthemselves vary too widely from the desired values, machine cycling willalso be stopped. For example, if the die temperature itself rises toohigh, R1 will be energized continuously while 56 is closed, and the dieclosing timer or control 58 will not be energized. Likewise, if the dietemperature should decrease too much, R2 cannot operate even thoughcontacts 68 of R1 will then have remained closed. The desired range ofsensing control is set by the value of resistor 50 relative to thesupply voltage, and particular circuit parts and parameters employed.

While the invention has been described herein in considerable detail inconnection with a preferred embodiment, it is to be understood that suchdetails are explanatory and not limiting, and that the scope of theinvention is as defined in the appended claims.

What is claimed is:

1. In a casting machine of the type having a pair of relatively movableplatens adapted to carry molding die blocks between open and closedpositions, injection means for supplying casting material to a cavitydefined by said die blocks, and a machine program control for openingsaid die blocks for ejection of a molded part and fdr thereafter closingsaid die blocks in preparation for a succeeding molding cycle, theimprovement comprising:

(a) radiant energy sensing means mounted relative to said platens torespond to the radiant energy flowing from the separated surfaces of theopened die blocks, and from any cast material in or between said blocks,

(b) a normally-open sensing circuit connected to said sensing means,

(c) means controlled by said program control for closing said sensingcircuit only during an interval following substantial completion of theopening movement of said die blocks, and

((1) means responsive to the output of said sensing circuit forsignalling the presence of unejected molded material in or about acavity formed by said die blocks.

2. A casting machine in accordance with claim 1, in which said radiantenergy sensing means is selectively sensitive to infra-red radiations.

3. A casting machine in accordance with claim 1, including at least onesource of infra-red radiation mounted on said machine in position toirradiate the parting face of one of said die blocks.

4. A casting machine in accordance with claim 1, in which saidnormally-open sensing circuit includes in series the normally-opencontacts of at least two relays, one

operated in response to the output of said radiant energy sensing means,and the other operated in timed relation after the expiration of anormal ejecting period following separation of said die blocks.

5. A casting machine in accordance with claim 1, including meanscontrolled by said sensing circuit, when completed, for interruptingfurther operation of said machine.

6. A casting machine in accordance with claim 4, including an additionalrelay (R1) connected for operation by said sensing means during aninitial phase of the opening of said die blocks, said additional relaywhen operated completing an operating and holding circuit for said onerelay (R2).

7. In a casting machine of the type having a pair of relatively movableplatens adapted to carry molding die blocks between open and closedpositions, injection means for supplying molten material to a cavitydefined by said die blocks, and a machine program control for openingsaid die blocks for ejection of a molded part and for thereafter closingsaid die blocks in preparation for a succeeding injection and moldingcycle, the improvement comprising:

(a) radiant energy sensing means mounted relative to said platens torespond to the infra-red energy flowing from the separated surfaces ofthe opened die blocks, and from any hot cast material in or between saidblocks,

(b) a normally-open sensing circuit connected to said sensing means,

(c) means controlled by said program control for closing said sensingcircuit only during an interval fol- 8 lowing substantial completion ofthe opening movement of said die blocks, and in dependence upon theoutput of said sensing means, and (d) means responsive to the output ofsaid sensing circuit for signalling the presence of unejected moldedmaterial in or about the cavity of said die blocks. 8. In a castingmachine of the type having a pair of relatively movable platens adaptedto carry molding die blocks between open and closed positions, injectionmeans for supplying molten material to a cavity defined by said dieblocks, and a machine program control for opening said die blocks forejection of a molded part and for thereafter closing said die blocks inpreparation for a succeeding injection and molding cycle, theimprovement comprising:

(a) radiant energy sensing means mounted relative to said platens torespond to the temperature of at least one of said die blocks, and

(b) means responsive to the output of said sensing means for signallinga departure of the temperature of the sensed die block away from apredetermined range.

References Cited by the Examiner UNITED STATES PATENTS 2,317,839 4/1943\Vestin. 2,794,926 6/1957 Watts et al. 25083.3 2,886,970 5/1959 Munker25083.3

J. SPENCER OVERHOLSER, Primary Examiner.

R. D. BALDWIN, Assistant Examiner.

8. IN A CASTING MACHINE OF THE TYPE HAVING A PAIR OF RELATIVELY MOVABLEPLATENS ADAPTED TO CARRY MOLDING DIE BLOCKS BETWEEN OPEN AND CLOSEDPOSITIONS, INJECTION MEANS FOR SUPPLYING MOLTEN MATERIAL TO A CAVITYDEFINED BY SAID DIE BLOCKS, AND A MACHINE PROGRAM CONTROL FOR OPENINGSAID DIE BLOCKS FOR EJECTION OF A MOLDED PART AND FOR THEREAFTER CLOSINGSAID DIE BLOCKS IN PREPARATION FOR A SUCCEEDING INJECTION AND MOLDINGCYCLE, THE IMPROVEMENT COMPRISING: (A) RADIANT ENERGY SENSING MEANSMOUNTED RELATIVE TO SAID PLATENS TO RESPOND TO THE TEMPERATURE OF ATLEAST ONE OF SAID DIE BLOCKS, AND (B) MEANS RESPONSIVE TO THE OUTPUT OFSAID SENSING MEANS FOR SIGNALLING A DEPARTURE OF THE TEMPERATURE OF THESENSED DIE BLOCK AWAY FROM A PREDETERMINED RANGE.